中建南盆地后扩张期T5和T3不整合面的发育特征及对南海科学钻探的意义-Characteristics of unconformity T5 and T3 in the Zhongjiannan basin and their significance for scientific drilling in the South China Sea during the post- spreading period

中建南盆地后扩张期T5和T3不整合面的发育特征及对南海科学钻探的意义

2022,96(8):2822-2832

王伟平¹, 姚永坚^2,3, 蔡周荣⁴, 殷征欣¹, 朱荣伟^2,3, 尉建功^2,3, 鞠东⁵

1) 自然资源部海洋环境探测技术与应用重点实验室，国家海洋局南海调查技术中心，广东广州， 510300;2) 南方海洋科学与工程广东省实验室(广州)，广东广州，511458;3. 3) 自然资源部海底矿产资源重点实验室，中国地质调查局广州海洋地质调查局，广东广州，510075;4) 中山大学海洋科学学院，广东珠海，519082;5.3) 自然资源部海底矿产资源重点实验室，中国地质调查局广州海洋地质调查局，广东广州，510075

摘要：中建南盆地是位于南海西部陆缘的一个走滑拉张型盆地，具有南海北部张裂和西部走滑的双重构造特征，盆地发育新生界多个区域不整合面，对于研究盆地的沉积- 构造演化史、油气资源以及南海的形成过程都具有重要意义。本文通过收集越南钻井约束，对广州海洋地质调查局的深反射地震剖面进行了重新解译，标定南海扩张结束后(中中新世以来)T5和T3两个区域不整合面的地质属性，结合区域构造运动分析，认为：T5不整合面形成于南海海底扩张停止时期的碰撞不整合面，对应于红河- 南海西缘断裂带从左旋运动到右旋运动的过渡期，时代为15 Ma，地震剖面揭示该界面总体的构造活动不强烈，推测沙巴造山运动在中建南盆地的响应已大幅减弱。T3不整合面对应于区域性重要板块重组事件和全球海平面快速下降的构造转换面，与红河- 南海西缘断裂带右旋走滑密切相关，时代为116 Ma，地震剖面显示该界面具有明显的剥蚀削截特征，同时是南海西部大规模碳酸盐岩、水道和扇体开始发育的重要时期，推测为南沙运动或万安运动在盆地内强烈作用的结果。研究表明，南海后扩张期表现出强烈构造活动及沉积响应的差异，通过未来大洋钻探，可明确南海西部T5、T3两个区域不整合面的空间变化特征和区域动力学环境，为认识南海西缘断裂带对西部沉积盆地群成因机制以及油气分布的控制作用提供依据。

关键词：中建南盆地；南海；不整合面；构造演化；科学钻探

Characteristics of unconformity T5 and T3 in the Zhongjiannan basin and their significance for scientific drilling in the South China Sea during the post- spreading period

Wang Weiping¹, Yao Yongjian^2,3, Cai Zhourong⁴, Yin Zhengxin¹, Zhu Rongwei^2,3, Wei Jiangong^2,3, Ju Dong⁵

1) Key Laboratory of Marine Environmental Survey Technology and Application, Ministry of Natural Resources South China Sea Marine Survey and Technology Center, State Oceanic Administration, Guangzhou, Guangdong 510300, China;2) Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou, Guangdong 511458, China;3. 3) Key Laboratory of Marine Mineral Resources, Ministry of Natural Resources Guangzhou Marine Geological Survey, China Geological Survey, Guangzhou, Guangdong 510075, China;4) School of Marine Sciences, Sun Yat- sen University, Zhuhai, Guangdong 519082, China;5.3) Key Laboratory of Marine Mineral Resources, Ministry of Natural Resources Guangzhou Marine Geological Survey, China Geological Survey, Guangzhou, Guangdong 510075, China

Abstract：The Zhongjiannan basin is located in the west continental margin of the South China Sea (SCS) and belongs to a strike- slip extensional basin. The basin has the dual structural characteristics of tension fracture in the northern SCS and strike slip in the western SCS. Several regional unconformities were developed in the basin inthe Cenozoic, which is of great significance to the study of sedimentary- tectonic evolution history, oil and gas resources and the formation process of the SCS. In this paper, we re- interpreted the deep reflection seismic profiles of Guangzhou Marine Geological Survey by collecting the drilling data of Vietnam, and recalibrated the geological attributes of two regional unconformity surfaces T5 and T3 in the post- expansion period of the SCS. Combined with the analysis of regional tectonic movement, it is proposed that the surface T5 belongs to collision unconformity surface, and mainly formed in the period of the seafloor spreading stop. This surface corresponded to the transition period from left- lateral movement to the right- lateral movement of the Red River- Western edge fault zone withan age of 15 Ma. The seismic profiles reveal that the overall tectonic activity was not strong in T5 period, reflecting that the response of Sabah orogeny in the Zhongjiannan basin had been greatly weakened. The unconformity T3 is a tectonic transition surface, which reflects regionally important plate reorganization event and a rapid decline of global sea level. This surface is closely related to the right- lateral strike- slip of Red River- Western edge fault zone, with an age of 11. 6 Ma. Seismic profiles show this interface has obvious denudation and truncation characteristics, which were the result of strong action of the Nansha Movement or the Wanan Movement in the basin during the important period when large- scale carbonate rocks, channels and fans began to develop in the western SCS. Our research indicates that there are significant differences in tectonic activity and sedimentary response during the post- spreading period of the SCS. The spatial variation characteristics and regional dynamic environment of the surfaces T5 and T3 in the western SCS can be clarified by ocean drilling in the future, which will provide a basis for understanding the controlling effect of Red River- Western edge fault zone of the SCS on the genetic mechanism of the western sedimentary basins and the difference of oil and gas distribution.

Key words：Zhongjiannan basin; South China Sea; unconformity surface; tectonic evolution; scientific drilling

收稿日期：2022-05-24

基金项目：本文为国家自然科学基金项目(编号 U20A20100、42106079)、南方海洋科学与工程广东省实验室(广州)人才团队引进重大专项(编号 GML2019ZD0201)和中国地质调查局项目(编号 DD20221719、DD20201118、DD20160138、DD20190368、DD20190366)联合资助成果。

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